In respect to pgtips, I read the links he posted... well, here is a quote about that dangerous virus.... note: you have to install by yourself:

"The Trojan horse poses as a codec to help users view pornographic videos, but in fact changes DNS server entries to direct surfers unwittingly to other websites. This could be for the purposes of phishing, identity theft or simply to drive traffic to alternative websites."

The problem with many users, even those who consider themselves very technical is that when it comes to computer security they are many many years behind the times.

Thousands of websites are hacked daily to serve up malware. The meme that only porn sites serve viruses and trojans is just that: a meme and a myth. It may have been true at some point, but it stopped being true years ago. In fact, buying digital consumer electronics from well known and reputable vendors like Samsung and Best Buy could also get you infected by malware. Most of the attack vectors today do not come from porn sites, despite what advanced users may repeat to one another on forums.

So like I said in the previous post, how do you know what you're installing is what it claims to be?